The present invention generally relates to diagnostic medical imaging apparatus and more particularly to a mammography machine that employs a near-infrared laser as a radiation source.
Cancer of the breast is a major cause of death among the American female population. Effective treatment of this disease is most readily accomplished following early detection of malignant tumors. Major efforts are presently underway to provide mass screening of the population for symptoms of breast tumors. Such screening efforts will require sophisticated, automated equipment to reliably accomplish the detection process.
The x-ray absorption density resolution of present photographic x-ray methods is insufficient to provide reliable early detection of malignant tumors. Research has indicated that the probability of metastasis increases sharply for breast tumors over 1 cm size. Tumors of this size rarely produce sufficient contrast in a mammogram to be detectable. To produce detectable contrast in photographic mammograms, 2-3 cm dimensions are required. Calcium deposits used for inferential detection of tumors in conventional mammography also appear to be associated with tumors of large size. For these reasons, photographic mammography has been relatively ineffective in the detection of this condition.
Most mammographic apparatus in use today in clinics and hospitals require breast compression techniques which are uncomfortable at best and in many cases painful to the patient. In addition, x-rays constitute ionizing radiation which injects a further risk factor into the use of mammographic techniques as most universally employed.
Ultrasound has also been suggested, as in U.S. Pat. No. 4,075,883, which requires that the breast be immersed in a fluid-filled scanning chamber. U.S. Pat. No. 3,973,126 also requires that the breast be immersed in a fluid-filled chamber for an x-ray scanning technique.
In recent times, the use of light and more specifically laser light to noninvasively peer inside the body to reveal the interior structure has been investigated. This technique is called optical imaging. Optical imaging and spectroscopy are key components of optical tomography. Rapid progress over the past decade have brought optical tomography to the brink of clinical usefulness. Optical wavelength photons do not penetrate in vivo tissue in a straight line as do x-ray photons. This phenomenon causes the light photons to scatter inside the tissue before the photons emerge out of the scanned sample.
Because x-ray photon propagation is essentially straight-line, relatively straight forward techniques based on the Radon transform have been devised to produce computed tomography images through use of computer algorithms. Multiple measurements are made through 360xc2x0 around the scanned object. These measurements, known as projections, are used to back project the data to create an image representative of the interior of the scanned object.
In optical tomography, mathematical formulas and projection techniques have been devised to perform a reconstruction function somewhat similar to x-ray tomography. However, because light photon propagation is not straight-line, techniques to produce cross-section images are mathematically intensive and invariably require establishing the boundary of the scanned object. Boundary determination is important because it serves as the basis for reconstruction techniques to produce interior structure details. Algorithms to sate do not use any form of direct measurement techniques to establish the boundary of the scanned object.
Addition information concerning the interior of the breast can be obtained when a scanner is able to acquire data resulting from illuminating the breast with different wavelengths or from acquiring information pertaining to light emitted by fluorescent materials introduced into the breast.
It is an object of the present invention to provide a scanner for a medical optical imaging device that uses a fluorescent marker to provide an enhanced identification of an abnormality within the breast beyond the inherent localized changes in optical scattering and absorption.
It is another object of the present invention to provide a scanner for a medical optical imaging device that provides for simultaneous acquisition of optical data at multiple wavelengths.
It is still another object of the present invention to provide a scanner for a medical optical imaging device that provides for simultaneous acquisition of data from at least two planes within the breast.
It is another object of the present invention to provide a scanner for a medical optical imaging device that provides for simultaneous acquisition of attenuation data and fluorescence data.
It is another object of the present invention to provide a scanner for a medical optical imaging device that provides for acquiring pre- and post-injection of a contrast agent, such as Indocynine Green (ICG) of both attenuation and fluorescence data and reconstructing the image from the difference between the raw data sets.
In summary, the present invention provides a scanner for a medical optical imaging device, comprising an illumination source positioned to direct emitted light into a breast positioned below a support surface; first and second groups of photodetectors positioned in an arc around the breast to simultaneously detect light emerging from the breast; and optical filters disposed in front of the first group of photodetectors to restrict the wavelength of light reaching the first group of photodetectors.
The present invention also provides an apparatus for imaging a breast, comprising a scanning chamber for receiving therein the breast to be scanned; a laser beam disposed within the scanning chamber for impinging on the breast, the laser beam being adapted to orbit around the breast; first and second groups of detectors positioned in an arc around the breast to simultaneously detect light emerging from the breast to generate first and second projection data, respectively; optical filters operably associated with the first group of detectors to restrict the wavelength of light reaching the first group of detectors to the wavelength of radiation emitted by a contrast agent introduced into the breast after being activated by the beam; and a computer to reconstruct an image of the breast from projection data derived from subtracting first and second baseline projection data prior to introduction of the contrast agent into the breast from respective first and second projection data obtained after introduction of the contrast agent.
The present invention further provides a method for collecting data for use in image reconstruction of a breast being scanned, comprising providing a beam of laser; providing a contrast agent within the breast; orbiting the laser beam around the breast clockwise to obtain a first set of projection data; orbiting the laser beam around the breast counterclockwise to obtain a second set of projection data; providing first and second groups of detectors positioned in an arc around the breast to detect light emerging from the breast to generate the first and second sets of projection data, respectively; restricting the first group of detectors to the wavelength of radiation emitted by a contrast agent within the tissue after being activated by said laser beam; and subtracting first and second baseline projection data obtained prior to introduction of the contrast agent into the breast from respective first and second projection data obtained after the contrast agent has been introduced to obtain respective differential projection data to be used in image reconstruction.
These and other objects of the present invention will become apparent from the following detailed description.